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Agronomy Journa l • Volume 110 , I s sue 5 • 2018 Forage producers in the southeastern United States rely heavily on cool season species, specifically non-native tall fescue [Schedonorus arundinaceus (Schreb.) Dumort.] (Ball et al., 1993). Despite strong persistence and production, TF has slow growth during mid-summer (Ball et al., 2007). A group of NWSG provides an alternative summer forage for producers, but adoption has been limited due to their lower nutritive value, shorter growing season, and high establishment cost compared to cool-season forage species. Another drawback is the fall rest period required to allow NWSG to build root reserves and resist cool season weed encroachment (Vogel and Bjugstad 1968; Owensby et al., 1977; Forwood and Magai 1992). The resulting dormant forage can be harvested or grazed, but has a large proportion of stem material and contains decreased CP content and greater fiber (Forwood and Magai 1992; Waramit et al., 2012). Forage with such poor nutritive value is not traditionally grazed or baled by livestock managers. Plant growth regulators which inhibit gibberellin synthesis offer a potential method to reduce stem elongation and improve grass digestibility (Rademacher, 2000). Therefore, late-summer application of a gibberellin inhibitor could improve nutritive value of fall grown NWSG forage. This could convert currently under-utilized forage into a resource for livestock managers during late fall and winter. Research has evaluated applications of paired gibberellin and nitrogen fertilizer to pastures (Whitehead and Edwards, 2015; Bryant et al., 2016; Zaman et al., 2016). Gibberellin application improves FM but reduces aboveground CP and increases NDF (Bryant et al., 2016). Gibberellin also has a notable side-effect of reduced root storage and tillering (Zaman et al., 2016). Since gibberellin application is a useful strategy to stimulate productivity at the expense of lower forage quality, gibberellin inhibition may be useful in forage management to improve forage nutritive value when FM production is not a priority (Sawyer et al., 2012; Baron et al., 2014; Raynor et al., 2016). The forage nutritive value reduction due to gibberellin is attributed to increased allocation to aboveground growth, diluting nutritive value such as CP and increasing fiber content. Therefore, suppressing the gibberellin pathway could improve nutritive value during long-term rest periods (1–2 mo.). Since NWSG currently require a rest period that results in low nutritive value forage but Improving Nutritive Value of Native Warm-Season Grasses with the Plant Growth Regulator Trinexapac-Ethyl